A Data Record of the Cloudy Boundary Layer

Objective: To create a science-driven multi-sensor multi-parameter earth system data record of duration 10+ years of observations and uncertainty characteristics of the subtropical cloudy boundary layer. In addition to aggregating existing level-3 products, unique elements of the record will include:

a unique climatology of warm rain from the CloudSat cloud profiling radar.

Motivation and Methodology: In 2007 the Intergovernmental Panel on Climate Change reiterated that clouds remain the largest source of uncertainty in climate projections. In this context, boundary layer clouds are thought to be the main reason for this uncertainty and to play a central role in cloud-climate feedbacks and interactions. These clouds are also important to the surface energy balance and Sea Surface Temperature (SST) distribution, and are key elements in biases in seasonal coupled model forecasts and simulated mean climate. Current climate and weather models are still far from realistically representing boundary layer clouds. A key problem is the lack of a coherent data record of cloudy boundary layer properties as measured from space. Motivated by this scientific focus, this project will address this key problem by creating the first data record uniquely focused on the cloudy boundary layer as seen from space. The goal is to produce a simple and easily used repository of diagnostic tools relevant to interpreting the key physical processes governing the cloudy boundary layer.

Recent state of the art satellite observations, particularly those from the A-Train sensors, allow for a more complete characterization of the cloudy boundary layer than ever before. Relevant observations include the cloud Liquid Water Path (LWP) from optical and microwave sensors, cloud height distributions from various sources including Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), Multi-angle Imaging SpectroRadiometer (MISR) and MODIS, Radiative fluxes from Clouds and the Earth's Radiant Energy System (CERES), cloud microphysics from MODIS, boundary layer height from the Global Positioning System, light precipitation estimates from CloudSat, key moisture and temperature variables from various sensors, and vertically resolved cloud occurrence from active sensors.

All of these parameters are of first order relevance to understanding the distribution and variability of boundary layer clouds. Furthermore the observations are considered to be of high quality in subtropical ocean regions, where many of the essential interactions are thought to occur. Therefore, we propose to create an earth system data record composed of observations relevant to the cloudy boundary layer that will provide the context to understand and model clouds in the boundary layer regimes known to be particularly sensitive to climate perturbations.